Open AccessBlack hole blackbodies
Author(s) -
King A. R.,
Puchnarewicz E. M.
Publication year - 2002
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1046/j.1365-8711.2002.05761.x
Subject(s) - physics , black body radiation , astrophysics , eddington luminosity , black hole (networking) , active galactic nucleus , galaxy , luminosity , schwarzschild radius , radius , astronomy , accretion (finance) , radiation , quantum mechanics , computer network , routing protocol , routing (electronic design automation) , computer security , computer science , link state routing protocol
Many black hole sources emit a substantial fraction of their luminosities in blackbody‐like spectral components. It is usual to assume that these are produced in regions at least comparable in size to the Schwarzschild radius of the hole, so that a measure of the emitting area provides an estimate of the black hole mass M . However, there is then no guarantee that the source luminosity (if isotropic) obeys the Eddington limit corresponding to M . We show that the apparent blackbody luminosity L sph and temperature T must obey the inequality L sph < 2.3 × 10 44 ( T /100 eV) −4 erg s −1 for this to hold. Sources violating this limit include ultrasoft active galactic nuclei (AGN) and some of the ultraluminous X‐ray sources (ULXs) observed in nearby galaxies. We discuss the possible consequences of this result, which imply either super‐Eddington or anisotropic emission in both cases. We suggest that the ultrasoft AGN are the AGN analogues of the ULXs.